JPS6044721A - Control method for mixing gaseous fuel - Google Patents

Abstract

PURPOSE:To simplify a control device and improve a controlling accuracy of mixing ratio, by utilizing a third gaseous fuel to compensate for a varying index of flow rate change of first and second gaseous fuels which are supplied under a controlled flow rate or a pressure. CONSTITUTION:While a control circuit 1 controls the flow rate of LDC for a converter, a control circuit II controls the flow rate of COG for a coke oven. The controlling function of control circuit III is as follows. That is, a CO concentration detector 38 is provided at a position in a branch pipe parting from a LDG piping, the position being close to a LDG holder, where a LDG has a gretly varying calorie. The CO concentration detector 38 functions to detect the concentration of CO contained in the LDG and transmit its detection to a ratio setting device 39. The ratio setting device 39 functions to compensate for an input signal from a flow meter 32 in response to an input signal from the CO concentration detector 38, and transmit to an adder 40 a control signal regarding the flow rate of BFG furnace gas, the control signal being obtained by multiplying a compensated signal by a preset ratio and having a WI substantially equal to the LDG flow rate. On the other hand, a flow meter 41 measures merely the flow rate of COG passing through a COG piping and having a minor variation of calorie, and transmits its measurement signal to a ratio setting device 42 and a watch index control device 46. The flow rate of BFG inputted to the ratio setting device 42 is feedback controlled by a feedback signal regarding the WI value, which signal being outputted from a control circuit IV.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling the mixing ratio of three types of gas fuels, and more specifically, a method for controlling the mixing ratio of three types of gas fuels so that an index such as the Wotsube index value is constant. Concerning how to control.

Blast furnace gas (BFG) is a by-product gas generated at steel plants.
), coke oven gas (COG), converter gas (L
DG) are well known. By-product gases are used alone or as a mixed gas in heating furnaces, etc.
When using a mixture of two types of by-product gases, the mixture can basically be controlled by controlling the ratio of the two types of gases, but the composition of each by-product gas can be changed depending on the blast furnace, coke oven, or converter. Since the amount of heat varies depending on the operation, the amount of heat cannot be kept constant by ratio control alone. Therefore, feedback control is also performed at the same time to keep the properties of the mixed gas, ie, the value of Wl, the calorie value, etc., constant.

Here, Wl is expressed by the following formula.

Wl-H/F However, H: Calorific value T: Density, and when mixing one more type of gas, i.e., when mixing three types of gases, control that executes the mixing control of the two types of gases in two stages. was being carried out. For example, as shown in Figure 1 (B
FG is branched into two flows, one BFG is mixed with l[lG by control circuit A, and the other BFG is controlled by control circuit A.
11 circuit B mixes with COG, and these two mixed flows (BFG +1, DG, BFG + COG) are controlled by 匍1ra circuit c and ji11 supply U circuit, respectively, and then mixed, and further three types of mixed gas are mixed. In order to make the Wl value appropriate, feed hack control is performed by the ni control circuit E.

To explain this in detail, the flow rate of 1 and DG supplied from the IU control LDG holder 1 of the control circuit A is measured by the flowmeter 2, and this measurement signal is multiplied by the ratio set by the ratio setting device 3t. is applied to the flow rate controller 4, and the flow rate controller 4 adjusts the valve 6 so that the LDG side branch flow rate of the liver G measured by the flow meter 5 matches the input signal from the ratio setting device 3.

Control circuit B measures the COG flow rate with a flowmeter 7, and multiplies this signal by the ratio set in the ratio setting device 8, and the flow is sent to the controller 9. The valve 11 is adjusted so that the COG side branch flow rate of the BFG measured by the flow meter 10 matches the input signal from the device 8. However, the ratio setting device 8 is set to a value necessary to keep the output value of the volution index controller 21 which measures and controls the wr value of the three types of mixed gas to be constant.

The control circuit C measures the pressure of the mixed flow of nFG and 12 ports G using pressure 8112 on the downstream side of the confluence point X in the BFG point 1.130 table, and sets this to the pressure controller 13. The pressure is adjusted by valve 14 to match the value.

The control circuit is controlled by measuring the flow rate of the mixed flow of BFG and LOG with the flowmeter 15, multiplying this by the ratio set in the ratio setting device 16, and transmitting it to the flow rate controller 17. ,! : flfl' of BFG 10 COD measured by flow meter 19 downstream of confluence Y with COG
The flow rate is controlled by the valve 18 so that a matches the input value from the ratio setting device 16.

The control circuit E controls the above flow in a total of 2. 5. ]0. 7
The Otsube index controller 21 calculates the WI value based on the signal regarding the total gas flow rate from , the pressure signal of the three-type mixed gas based on the pressure n122, and the temperature signal based on the temperature a123, and converts this into a pre-given value. The control signal to be output is sent to the ratio setter 8 and is mixed with the COG.
Feedback is provided to control the amount of FG.

In this way, in the conventional method, five control circuits are required to mix three types of gas and keep the woad index value of the mixed gas constant.
Since the secondary mixing control was performed, followed by the secondary mixing control and two-stage mixing control by the control circuit C-D, and the overall feedback control was performed by the control circuit E, the fluctuations in this control system were naturally large. However, the control accuracy was not good, and the control device itself was complicated.

The present invention has been made in order to eliminate the drawbacks of such three types of gas fuel mixture control, and its purpose is to change the two-stage mixture control to one-stage control, thereby simplifying the control device, Another object of the present invention is to provide a method for controlling the mixing of three types of gas fuels, which can improve the accuracy of controlling the mixing ratio.

The gas fuel mixing control method according to the present invention is a method for controlling the supply of each gas fuel to keep a predetermined index of the mixed gas fuel constant when three types of gas fuels are supplied separately and mixed. First, by controlling the pressure. supplying the second gas fuel; Supplying the third gas fuel in an amount that is the sum of the respective flow rates of the third gas fuel required to compensate for the fluctuations in the index for each gas fuel due to the flow fluctuations of the respective second gas fuels. Well, first. Second. It is characterized by mixing a third gas fuel.

The present invention will be specifically explained below based on the drawings.

FIG. 2 is a schematic diagram that does not show the implementation state of the present invention, and 1 is an L
It is a DG holder. LOG stored in LOG holder 1
is 1. by the pressurizing machine 30. The COC flowing through the DG pipe is adjusted in flow rate by the control circuit I and sent to the confluence point Z of the three types of gas fuels, and the COC supplied from the COG supply source (not shown) is adjusted in flow rate by the control circuit II. The flow passes through the COG pipe and is sent towards the confluence point Z, and further flows through the BF (not shown).
The flow rate of the BFG supplied from the G supply source (Jζ) is adjusted by the control circuit ■ which also uses the feedback value from the control circuit ■ as an input signal to make the WI value of the three-type mixed gas fuel appropriate The gases 1 and 37M are mixed at the confluence point Z and sent to a heating furnace (not shown) or the like.

The control circuit 1 in the device used in the present invention configured as described above. The control details of IT, FIT, and IV will be explained next. To control the control circuit I, a flow meter 32 is installed on the upstream side of the valve 34 provided in the middle of the LflG piping, the flow rate of I and DG is measured by the flow meter 32, and the measurement results are sent to the flow rate controller 33 and the ratio described later. The flow rate controller 33 controls the LDG flow rate by adjusting the opening degree of the valve 34 so that the input signal from the flow meter 32 matches the set value. .

Regarding the control of the control circuit H, a pressure gauge 35 is attached to the downstream side of the valve 37 provided in the middle of the COG piping, and the pressure a135
The pressure on the downstream side of the valve 37 is measured, the measurement result is sent to the pressure controller 36, and the pressure controller 36 adjusts the opening degree of the valve 37 so that the input signal from the pressure gauge 35 matches the set value. COG flow rate control is performed by this.

Control of control circuit (2) is performed as follows. In other words, in LOG where the calorie value fluctuates greatly, the LDG pipe should be branched off from the pipe near the LDG holder 1.
An oIM degree detector 38 is attached, the COS degree in the LOG is detected by the coa degree ratio detector, and the detection result is provided to the ratio setter 39. Is the ratio setting device 39 co? a degree detector 3
Compensate the input signal from the flowmeter 32 based on the input signal from 8, multiply the compensated signal by a preset ratio,
The obtained signal, that is, the control signal regarding the BFG flow rate where WI is approximately equivalent to the LIIG flow rate, in other words, the CO
When the a degree is high, the flow rate of BFG with a small calorie value is the standard co: BFG corresponding to the LDG flow rate at the a degree level.
'Iff, . If the CO concentration is low, the BFG flow rate sends to the adder 40 a signal related to the IIFG flow rate that is smaller than the BFG flow rate corresponding to the LDG flow rate at the reference CO concentration level. -For COG that flows through 10,000 COG pipes and has little calorie fluctuation, only the flow rate is measured.
The signal measured by the flow meter 41 is provided to a ratio setter 42 and a water tube index controller 46. Further, a feedback signal regarding the WI value from the control circuit (2), which will be described later, is provided to the ratio setter 42. Ratio setter 42
compensates the input signal from the flowmeter 41 based on the feed bank signal from the control circuit ■, multiplies the compensated signal by a preset ratio, and calculates the obtained signal, that is, Wl is approximately equal to the COG flow rate. A control signal related to the equivalent BFG flow rate, in other words, when the WI value is high, the I'lFG flow rate with a small caloric value is larger than the BFG flow rate corresponding to the COG flow rate at the standard W rubel, and conversely, the WI value is low, the BFG flow rate sends a signal to the adder 40 regarding the BFG flow rate smaller than the BFG flow rate corresponding to the COG flow rate of the standard W rubel. The adder 40 adds the two input signals regarding the BFG flow rate, and provides the obtained added signal to the flow rate controller 43, which adjusts the valve 44 based on the input signal to control the BFG flow rate and adjust the flow rate. Feedback control is performed based on signals from a total of 45 units. The measurement signal from the flow meter 45 is also given to a water tube index controller 46 .

Regarding the control of the control circuit (2), the water index controller 46 inputs the total gas fuel flow rate from the flow meters 32, 41, and 45 and the pressure gauge 47. A WI value is calculated based on the above equation from the pressure signal and temperature signal measured by the thermometer 48, and a control signal is sent to the ratio setter 42 of the control circuit (2) so that the calculated value becomes a predetermined WI value, and the BFG flow rate is feedback control.

In the above explanation, the merging point is set at one location, but the present invention is not limited to this, but mixes two types of gas fuel after control,
There may be two locations where the remaining one gas fuel is mixed, and although control is performed to keep Wl constant, the present invention is not limited to this, and control regarding calories or other indicators may also be performed. Of course.

Next, the effects of the present invention will be explained. Regarding the calorie fluctuation of by-product gas, BFG is 730±50kcal/N n
? .

COG 4600±100kcal/N rrr
, 2000±300kca]/Nrd in LOG, and the calorie fluctuation of each gas is quite large. When such by-product gases were mixed and controlled by the conventional method using a two-stage control circuit, the variation in the calorific value of the three types of mixed gas was extremely large, but using a device with a single-stage control circuit was used. According to the present invention, the fluctuation can be reduced by about 30%, and the operation of heating furnaces etc. using this gas has become stable.

Furthermore, the 1st rI! J. As shown in FIG. 2, compared to the apparatus used in the conventional method, the apparatus used in the present invention can reduce the number of devices and the manufacturing cost.

It goes without saying that the present invention can be used even when two types of gas fuels are mixed.

As described above in detail, the gas fuel mixing control method according to the present invention controls the flow rates of the three types of gas fuels in one stage and then mixes them, so a complicated piping configuration and a complicated control method are not required. It is possible to simplify the process and improve the accuracy of mixture control, etc.
It has excellent effects on reducing the amount of mold equipment used in the tlilJ control equipment and stabilizing the operation of subsequent processes.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a control device of a conventional method, and FIG. 2 is a schematic diagram not showing an implementation state of the method of the present invention. 34.31.44...Valve

Claims (1)

[Claims] 1. When supplying and mixing three types of gas fuel separately,
In the method of controlling the supply of each gas fuel to keep a predetermined index of the mixed gas fuel constant, the first. supplying the second gas fuel; Supplying the third gas fuel in an amount that is the sum of the respective flow rates of the third gas fuel required to compensate for the fluctuations in the index for each gas fuel due to the flow fluctuations of the respective second gas fuels. Well, first. Second. A gas fuel mixing control method comprising mixing a third gas fuel.